Since the 1970's there has been a great need to use rapidly moving doors in buildings for industrial use. This applies to openings indoors as well as in external walls, where the door provides shielding between different activities or prevents drafts and heat losses. Presently, rolling doors with flexible door leaves are used for this purpose, but also more rigid constructions like slatted doors with polymeric or metallic lamellae are used. These doors are rolled up on an overhead drive cylinder and can be provided with additional elements like a weight balance system, tensioning system, windows or the like. For safety reasons, rolling doors can be provided with safety edge protection, failsafe devices, drop protection, etc.
As understood from the above, rollup doors are available in different styles and materials. In one traditional design the door leaf is rolled up on a shaft directly upon itself. The drawback with this construction for more rigid doors is that wear soon causes visible marks on the lamella surface, which is regarded as a negative factor. In addition the lamellae are rolled on each other without any padding, which causes noise. These doors are normally run at low opening and closing speed in order to overcome this.
A flexible door leaf with, for example, sensitive material such as PVC, can also suffer from these wear problems. U.S. Pat. No. 5,307,859 discloses that this can be overcome by applying additional flexible strips extending perpendicular to the driving shaft. When the curtain is rolled or folded in its retracted position, the separation strip rolls or folds on itself to hold the layers of the curtain apart from one another.
U.S. Pat. No. 5,484,007 describes a slatted door comprising two guide tracks situated on opposite sides of the door opening. The guide tracks extend vertically over approximately the height of the door opening, and then merge at the entrance of the door into an inwardly positional spiral, so that the slats of the door run essentially free of each other, thereby providing a high speed door. This design requires guiding channels approximately twice as long as the door height. The lamellae, rolls, and guiding system are in motion during the complete opening/closure operation, which causes increased wear and noise.
A related door construction is disclosed in WO 01/69032 which overcomes the above-described disadvantages by providing a chain of support bodies screwed onto the side of the lamellae. These links are thicker than the lamellae. During the roll up operation, these support bodies roll upon each other and create a distance between the lamellae. In order to create an even roll, the links are curved according to an average roll up diameter. Still, this door design has a disadvantage in that the rolled up layers are in direct contact with each other, which causes noise. Also, an increased diameter is necessitated. The support bodies are rolled upon each other on an irregular surface, which is only partly compensated by the arched geometry. This top-on-top rolling leads to the support bodies suffering from both tension and pressure, and both outer surfaces incur wear and tear.
U.S. Pat. No. 5,682,937 describes a closure comprising a deformable rolling blind or shade and a drum formed by two parallel shafts, which are situated transversely in the upper position substantially superposed to the axis of the blind or shade. The upper edge of the blind or shaft is joined to the first shaft. The second shaft is joined to the first shaft and free to rotate, when the first shaft is driven by a drive mechanism and is free to rotate, at a slightly different speed than the first shaft. This provides a winding mechanism in which successive layers or turns of the shade or blind do not come into contact to each other avoiding an erratic unwinding of the shade or blind. The patent also describes a shade or blind in which the separation of the successive layers or turns is achieved by having stepped pulleys mounted on each end of the shafts having cheeks of different diameters to selectively form bearings with the ends of the slats of the shade or blind. The separation may also be achieved by the cheeks of the two superimposed shafts forming a bearing with end pieces attached to the slats of the shade or blind and extending at different lengths from the slats. The separation of the slats of the shade or blind may be obtained by rollers of different diameter attached to the ends of the slats, co-operating in reverse with independent tracks having the same diameter borne by the ends of the superimposed shafts. The disadvantages with this winding principle are the need for multiple shafts, and a low winding speed, as the shade or blind has to pass around the several shafts.